#include "common.h"

int takeAttendance(vector<int>& records)
{
	if (records[0] != 0) return 0;
	int left = 0;
	int right = records.size() - 1;
	while (left < right)
	{
		int mid = left + (right - left) / 2 + 1;
		if (records[mid] == mid) left = mid;
		else right = mid - 1;
	}
	return left + 1;
}